Cook sweet potatoes in boiling water for 30 to 45 minutes or until tender. Drain and let cool to touch; peel and mash. Combine together the sweet potatoes, 1/2 cup of brown sugar, eggs, vanilla, half-and-half, and butter. Beat at medium speed until smooth. Spoon into greased 13 x 9 baking dish. For the topping, combine 1 cup of brown sugar and flour; cut in butter with pastry blender until mix is crumbly. Stir in pecans; sprinkle mixture over casserole. Bake uncovered at 350° for 30 to 35 minutes or until lightly browned and bubbly around edges. Serves 8.

Note: This recipe can be prepared ahead and chilled overnight. Add 5 minutes to bake time.